INTERVIEW: Reaching into the Rhizosphere – Root Studies Impacting Commercial Peach and Citrus

Scott Trimble

June 29, 2021 at 10:57 am | Updated March 9, 2022 at 1:38 am | 8 min read

University of Florida Plant Root Biologist Dr. Lorenzo Rossi sits down with CID Application Scientist Galen George to discuss commercially impactful root research on Florida peach cultivation, and HLB-affected citrus trees using the CI-602 Narrow Gauge Root Imager.


Dr. Lorenzo Rossi is an Assistant Professor affiliated with the Horticultural Sciences Department and located at the UF/IFAS Indian River Research and Education Center (IRREC) in Fort Pierce, FL. His main research area is in plant root biology. Dr. Rossi’s research program focuses on improving root health and growth on HLB-affected citrus, leading to the development of environmentally sound and effective citrus management methods. Particularly, his field and greenhouse trials aim to study the root system architecture of HLB-affected citrus root stocks, as well as, specialty crops such as peaches and pongamia trees. Dr. Rossi’s laboratory is equipped with instruments needed for the study of root functions and architecture, root traits, root physiology and root imaging.

Dr. Rossi coordinates the UF/IFAS Plant Root Science Consortium, under the Center for Stress Resilient Agriculture. He develops and provides seminars and field days to students and growers, and he is the lead instructor for the “Root and Rhizosphere Ecology” (HOS 6355) and “Advanced Horticultural Physiology” (HOS4341/HOS6932) courses in the Horticultural Sciences Department. He is also involved in organizing and teaching the “Planting Roots for the Future” international short summer course (ALS5932) which is held every year in Orlando, FL.

Prior to Dr. Rossi’s appointment at UF/IFAS, he completed two post doctorate positions: Texas A&M University and North Carolina State University. Originally from Italy, he received his Ph.D. Degree in Plant Biology from Italy’s most prestigious scientific university, Scuola Superiore Sant’Anna in Pisa, Italy.

Further information and related research can be found HERE.


Galen:    Great to see you again Dr Rossi. It’s been a little while, but it’s good to see you again. My name is Galen, and I’m an application scientist at CID Bio-Science, and my background’s in food science. And so, we’re really excited to talk to you today, Dr Rossi. So, if you could tell us a little bit about yourself. Tell us about your background and how you came to be where you are and why you chose this specific area of research, and then we’ll get right into the nitty-gritty of what you’ve been doing lately.

Lorenzo:    Alright, well, thank you for having me. My name is Lorenzo Rossi and I’m an Assistant Professor of Plant Root Biology at the University of Florida. I’m located off campus, so we are on a research station on the East Coast of Florida, and we work a lot on grapefruit and citrus in general, citrus roots, growth, and development. And actually, it was during my post-doc that my – my PhD was in plant biology – and during my postdoc I started working on roots. So, how roots of cultivated species react to pollutants. We were doing a lot of heavy metals, we were doing a lot of emerging pollutants such as nanoparticles. And with this I gained expertise on root growth and development under different conditions – environmental conditions. And there was an opening for a plant root biologist here at the University of Florida, here where I am right now. It’s been 4 years now, so I’m very pleased. I’m happy.

And why do root biology on citrus? Because there is a disease that is called citrus greening. We have been dealing with that for almost 15 years now. It came in 2005. It is a bacterium, and it replicates inside the roots and the vascular system of the phloem of the citrus trees. So, if we can better understand how we can measure root traits, root growth and development, we can prolong, or we can extend the lifespan of each of the citrus greening affected trees.

[Micronutrients + Citrus Greening (HLB)]

Galen:    Yeah, so we talked a little bit about this in our webinar that we did previously for the root scanner. Since then, how have things gone? How has work progressed in the field so far? Have you learned anything new that is particularly interesting about citrus greening?

Lorenzo:    So, we have a couple of projects on that using the minirhizotron. One of those projects – that’s the one that is more advanced too, it is the third year that we are doing it – we are seeing the micronutrients, particularly boron and zinc, have an effect on root growth, and an effect on the citrus greening itself. So, they’re actually – I don’t want to say antibacterial, but they have an effect on reducing the infection. And so, we saw that an increased amount of boron and zinc actually has a beneficial effect on our roots, and we are wrapping up that research. I have a graduate student who is about to graduate, so there will be some papers out soon. And what we did, we were applying different rate of the micronutrients, and we were measuring root growth with the minirhizotron every 4 months.

Galen:    So, with this project – and so you mention you’re using the CI-600 root scanner – what other technologies are you considering using for this project? Were you considering other technologies? And why would you choose to use this particular technology with the minirhizotron system as opposed to other methods of root analysis?

Lorenzo:    So, we are using the CI-602 actually.

Galen:    Oh, 602, yeah, that’s right.

Lorenzo:    But, so we choose this method because it’s non-destructive. So, as you know better than me probably, measuring root traits in the field is always challenging because you can go with traditional methods, so you can do excavations, you can dig holes in the field. But they are all destructive. So, if you have a commercial grove, it’s going to be challenging for you to find a farmer or producer that will like to go there and excavate roots or kill trees to measure root growth and development every 4 months. So, the minirhizotrons are really, really effective for us, because they are non-destructive, they stay in the soil for a long period of time, and you can always put the camera whenever you need to and take pictures.

What we are considering now is a little change in the experimental design. So, instead of just one tube per tree, we may want to increase that because we like to have a more full picture of the entire root system. And sometimes, with our irrigation system, most of the roots may grow in a direction that is nowhere near the tube.

Galen:    Oh yeah.

Lorenzo:    So, it is hit and miss sometimes. So, we are trying to add more tubes, at least 2 or 3. That’s what I’m working on next, that grant. And the other thing is, I think it will be important to have a better representation, not just of the root system, but also to see what’s going on in the upper level of the plants, and eventually sub-flow measurements. More roots means that there is more sub-flow going– there’s more flow going. Stomatal conductance can be another thing that we are willing to see. So, making more correlation–if the roots are bigger and they’re growing better, is there something that is correlated to more uptake of nutrients and water? More stomatal conductance? That would be our next level.

Galen:    Yeah, so taking a more holistic approach and getting a big picture of everything that’s happening within that particular tree. So, you’ve made these discoveries about the micronutrients; Are you planning on continuing the micronutrient study with other micronutrients? Or, what’s the next phase of your study?

Lorenzo:    We are still continuing that. There is a lot of interest from the industry. Of course, we want to give them some guidelines, and at the same time we need to be careful on what we are saying because, you know, they’re micronutrients. So, you don’t want to go out on the extension paper and say micronutrients will save your industry, because then you will have all the producers applying these big quantities to see if they can make a big tree. So, we need to know the exact amount of different types of cultivars, root stock, soil type. And the other thing, I want to see how they are affecting the soil. So, we just started a new project with a PhD student studying microbiome, so are they affecting the microbes? Are we seeing changes in the microbial community? And how this relates to root growth too. So, we have another project we started last year. Again, minirhizotron, but also, we were doing root growth, but also microbes and microbiome. So, that’s something we started last year. So, really I want to see a couple of seasons.

Galen:    Well, that’s going to be really interesting to see if they’re having a…you know, you might be eliminating some of the bacteria that you don’t want to see that’s causing the greening. But then you could also be eliminating a lot of the good bacteria that you need.

Lorenzo:    That’s right. I want to make sure we are not changing too much the rhizosphere ecology, so the big picture, because in the long-term you may be fixing the problem, you make create like 300 more.

Galen:    Right.

Lorenzo:    So, it’s always about the balance.

[A Window for Florida Peaches]

Galen:    It’s really great to see that you guys are already thinking ahead about that and making sure that you’re not going to, you know, you could fix greening in the short-term, but maybe it’ll come back, and maybe because you’re just completely sterilizing your soil there’s nothing left in there. So yeah, that’s great to see. So, any other really interesting aspects of this project, or other projects that you’re going to start working on soon that you want to talk about?

Lorenzo:    We are using minirhizotron for another project that’s on peaches. So, with the decline of the citrus industry in Florida we saw a lot of interest in specialty crops, and peaches is one of those crops. The main idea is we can beat the market a couple of weeks because, you know, once you have Georgia and South Carolina, they will eat the market in the southern region. I mean there is no interest from Florida peaches anymore. But we have that window – a couple of weeks, sometimes 3 weeks, so it’s mostly a month – in which we sell Florida peaches. So, we are working on that. And what was the problem there? So, in Florida we have 3 types of soils. So, we have soils that are deep, and the drainage is really good in the central region of Florida. But also, we have soils in the coastal area that they have a clay… a clay hardpan that is really, really hard to break, and they have plotting problems. So, we are trying to see, and we are working with breeders, to have root stocks that can survive well in our soil, coastal soil with lots of flooding. So, we selected a couple of new root stocks from some selections. We are working with breeders at main campus. And I have a PhD student who planted those trees in our soils, and we want to see with the minirhizotron if the root system is shallow or if it goes too deep. So, the root system architecture in this case, to see if we can breed a good root stock for our soil in the coastal region.

Galen:    Yeah. So, just from your two studies that you’re doing, a lot of really big, commercial impacts just from looking at these roots. You know, with trying to mitigate the greening, and then also trying to get an early start on the Florida peach harvest. So, that’s really, honestly really insightful that these research tools are going to be impacting things on the more commercial level. So, that’s great to hear. Yeah, so that’s all I have for you for today. If there’s anything else that you think that you want the public to know about–projects that you’re working on. Or if you have information about where they could see research or see what you’re working on next, then let us know, and we can also post links on that as well when we go to post this interview. But yeah, thank you so much, Dr Rossi. I really appreciate your time and it was great to catch up with you. Glad to see that the research is progressing really well, and yeah, I hope we can hear more from you in the next, you know, year. We’ll see some even more advancements with the micronutrient study, so that’s really cool. I’m really excited to see more about that.

Lorenzo:    Alright, well, thank you.

Galen:    Yeah. Thank you so much for your time Dr Rossi. Have a great day.

Lorenzo:    You too.

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